It is desired for light-sensitive photographic materials to have high sensitivity and to be easy to handle. In particular, with the recent progress of various photographic techniques, there are demands for more higher sensitivity in the respective fields. For example, there are demands for higher speed shuttering in cameras, demands for speedier processing in processing techniques for color and black-and-white films or photographic papers, demands for employment of electronics and for simplification in printing industries or the like, demands for improvements of various diagnostic abilities by X-ray photography and for lessened irradiation dose of X-rays in medical fields, and so on, and thus it is needed to make higher the sensitivity in complience with these demands in the respective fields. Also, in light-sensitive silver halide photographic materials, it is desired to lessen as much as possible the amount of silver to be used, from a viewpoint of the cost reduction or the resource saving, and it is needed also in this respect to make higher the sensitivity. With increase in the sensitivity, the less amount of silver can be used, whereby it becomes possible to save silver.
On the other hand, the light-sensitive photographic materials are often used in the shape of a film, using a synthetic resin as a support, and therefore sometimes tend to be folded for any reasons to cause the blackening of images after development, or cause the desensitization. Thus, as images after development may have been damaged, it must be prevented as far as possible that pressure is applied before development processing to produce the blackening at the portion to which the pressure has been applied (i.e., pressure marks), or that the desensitization takes place (i.e., pressure desensitization). Particularly in recent years, there have been made progress in various kinds of automization (for example, automatic driving systems, or automatic loading system of cameras, etc.), and therefore there is a great possibility that mechanical pressure is applied to the light-sensitive material before the development to cause the deterioration of the images. Also, in the case of X-ray films for medical use, the film size is so large that the so-called knick-mark which may occur when a film is folded during handling, thereby causing the pressure marks or the pressure desensitization. Since photographs for medical use serve as the bases of diagnoses and also judgement is made based on a delicate image appeared, the deterioration of images like this must be prevented.
However, this problem becomes much greater if the sensitivity is being made higher in complience with the demands as mentioned above. This is because the pressure marks or the pressure desensitization may become liable to occur as the sensitivity is made higher. Accordingly, in the resent state in the art, what is sought after is a light-sensitive photographic material having high sensitivity and yet being free from any pressure marks or pressure desensitization. However, it is considerably difficult to satisfy these both needs. Although many attempts to make higher the sensitivity have been made or various techniques for increasing the pressure resistance have been proposed, there has not been known any technique that can sufficiently satisfy both of these.
For example, the techniques for decreasing the pressure desensitization are disclosed in U.S. Pat. Nos. 3,655,390 and 3,772,032, and British Pat. No. 1,307,373. These techniques, however, tend to give influence to the sensitivity or the fog. Other than these, there are techniques disclosed in U.S. Pat. Nos. 3,655,390, 3,445,235 and 2,628,167, which, however, involve similar problems of desensitization or the like.
For another example, materials having excellent pressure resistance can be obtained according to the technique disclosed in Japanese Patent Examined Publication No. 48747/1985, which, however, may worsen the pressure blackening (fog) if the content of silver iodide (i.e., the content of AgI at the initial stage of a reaction system) is increased for the purpose of making the sensitivity higher.
Thus, no satisfactory light-sensitive materials have been available in the prior arts.